1. Technical Field
The present invention relates to a technology for controlling an electro-optical element such as an organic light-emitting diode (OLED) element or the like.
2. Related Art
Generally, electro-optical devices with a plurality of electro-optical elements have been widely used. Each of the plurality of electro-optical elements is disposed so as to correspond to any one of a plurality of data lines, and a gray-scale level of each electro-optical element is controlled on the basis of a voltage applied to the corresponding data line. Each of the data lines is commonly connected to a signal line through a switching element disposed so as to correspond to the data line. This signal line is supplied with a gray-scale signal which becomes a voltage in accordance with a gray-scale level of the electro-optical element with a predetermined cycle. The switching elements are sequentially turned on by means of pulse signals (hereinafter, referred to as ‘sampling pulses’) which sequentially become active levels for every predetermined period (hereinafter, referred to as ‘sampling period’), so that gray-scale signals are distributed to the corresponding data lines. As a result, a voltage of each of the data lines becomes a voltage in accordance with a corresponding gray-scale signal.
In this structure, if a period for which a gray-scale signal maintains a level in accordance with a gray-scale level of one electro-optical element and a sampling period with respect to the gray-scale signal are entirely coincident with each other on the time base, a predetermined voltage can be applied to each of the data lines. However, the gray-scale signal may be delayed with respect to the sampling period because of various factors such as a blunt waveform and a voltage drop in the signal line. In this case, since a level of the gray-scale signal varies within one sampling period, the predetermined voltage cannot be applied to each of the data lines. As a result, there is a problem in that irregularity of a gray-scale level (that is, a ghost) occurs along each of the data lines.
As technologies for solving the above-mentioned problem, each of JP-A-5-241536 (FIGS. 1 and 2 in JP-A-5-241536) and JP-A-9-212133 (FIGS. 1 and 2 in JP-A-9-212133) discloses a structure in which each of sampling pulses SMP[j] (j is a natural number) sequentially becomes an active level at a gap D, as shown in FIG. 18. According to this structure, since a gray-scale signal is not sampled by any switching element for a period reaching from an end point of a sampling period Ps to a start point of another sampling period Ps subsequent to the sampling period Ps, even when the gray-scale signal is delayed as shown by ‘Dg (delayed)’ in FIG. 18, a delayed amount is within a range of a time length of the period D, so that it is possible to prevent a voltage error of the data line from being generated due to a variation of the gray-scale signal.
However, according to the above-mentioned technologies, the time length in which the gray-scale signal is sampled to the data line must be reduced by the gap D. Accordingly, in a case in which the gray-scale signal should be supplied to each of the data lines with a short cycle (for example, in a case in which the total number of the data lines is large), the sufficient gray-scale signal cannot be supplied to each of the data lines, so that it is difficult to control a gray-scale level of each electro-optical element with high precision.